Radio personal communications system and method for allocating frequencies for communications between a cellular terminal and a base station

ABSTRACT

Transceiver frequency and optionally power level are allocated to a radio personal communications system which includes a base station connected to a wire telephone network and a cellular terminal operating within a region of a wide area cellular network to minimize interference between communications over the wide area cellular network and communications between the base station and the cellular terminal. The same cellular terminal may thus be used to communicate over the lower cost wire network when within range of the base station and over the wide area cellular network otherwise. The frequency for communications between the cellular terminal and the base station are optionally assigned by the operator of the wide area cellular network so appropriate frequencies and power levels can be assigned for base stations, to minimize same channel interference with the wide area cellular network.

This application is a continuation of application Ser. No. 08/148,828,filed Nov. 4, 1993, now U.S. Pat. No. 5,428,668.

FIELD OF THE INVENTION

This invention relates to communications systems and more particularlyto radio personal communications systems for use within wide areacellular networks.

BACKGROUND OF THE INVENTION

Radio communications systems are increasingly being used for wirelessmobile communications. An example of a radio communications system is acellular phone network. Cellular radio communications systems are widearea communications networks which utilize a frequency (channel) reusepattern. The design and operation of an analog cellular phone system isdescribed in an article entitled Advanced Mobile Phone Service byBlecher, IEEE Transactions on Vehicular Technology, Vol. VT29, No. 2,May, 1980, pp. 238-244. The analog mobile cellular system is alsoreferred to as the "AMPS" system.

Recently, digital cellular phone systems have also been proposed andimplemented using a Time-Division Multiple Access (TDMA) architecture.Standards have also been set by the Electronics Industries Association(EIA) and the Telecommunications Industries Association (TIA) for anAmerican Digital Cellular (ADC) architecture which is a dual mode analogand digital system following EIA/TIA document IS-54B. Telephones whichimplement the IS-54B dual mode architecture are presently being marketedby the assignee of the present invention. Different standards have beenpromulgated for digital cellular phone systems in Europe. The Europeandigital cellular system, also referred to as GSM, also uses a TDMAarchitecture.

Proposals have recently been made to expand the cellular phone networkinto a radio personal communications system. The radio personalcommunications system provides mobile radio voice, digital, video and/ormultimedia communications using radio personal communications terminals.Thus, any form of information may be sent and received. Radio personalcommunications terminals include a radio telephone, such as a cellulartelephone, and may include other components for voice, digital, videoand/or multimedia communications.

A radio personal communications system includes at least one telephonebase station also referred to herein as a base station. A base stationis a low power transceiver which communicates with a radio personalcommunications terminal such as a cellular telephone over a limiteddistance, such as tens of meters, and is also electrically connected tothe conventional public wire network. The base station allows the ownerof a radio personal communications terminal to directly access the wirenetwork without passing through the cellular phone network, whose accessrates are typically more costly. When located outside the range of thebase station, the personal communications terminal automaticallycommunicates with the cellular phone network at the prevailing accessrates.

A major problem in implementing a radio personal communications systemusing a common frequency allocation for both the base station and thecellular phone network is the frequency overlap between the cellularphone network and the base station. As understood by those having skillin the art, only a limited number of frequencies are available for radiocommunications. In the United States, cellular phone networks have beenallocated 832 30 kHz wide channels. Within this spectrum, each regionalprovider can substantially allocate and use these frequencies as it seesfit. Additional ranges of frequencies are also being allocated in theUnited States for use as wide area cellular communications networks.

Cordless phones, such as those used by individuals in their homes,utilize a separate range of frequencies, in the United States from 46MHz to 49 MHz. Therefore, they are able to operate within a cellularnetwork without interference. However, such phones are unable to operateas cellular phones connected to the cellular network when out of rangeof their individual base stations. Dual mode phones which operate bothas a cellular phone within the cellular frequency range (824-894 MHz)and as a conventional cordless phone (46-49 MHz) are described in U.S.Pat. No. 4,989,230 to Gillig et al.

Frequency overlap between the network and the base stations can beprevented if the network and base stations are allocated different bandsof frequencies as with the dual mode cellular and cordless phonediscussed above. However, such a hybrid system is not an efficientallocation of the frequency spectrum. Moreover, a hybrid personalcommunications terminal may be more expensive and complicated becauseadditional circuitry may be required.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide animproved radio personal communications system including a base stationand a cellular terminal and methods for using the same.

It is another object of the present invention to reduce frequencyoverlap in a radio personal communications system without the need for ahybrid communications system.

In the present invention a base station connects a wire telephonenetwork to the cellular terminal within a local region of a wide areacellular network. The base station includes a housing, which ispreferably portable, and a wire telephone network connector extendingwithin the housing for connecting the base station to the wire telephonenetwork. Activation means within the housing is also electricallyconnected to the wire telephone network connector for detecting anincoming call on the wire telephone network. A radio transceiver withinthe housing is responsive to the activation means for communicating withthe cellular terminal using a selected frequency within the spectrum ofthe wide area cellular network when the cellular terminal is withinrange of the base station. When the cellular terminal is not within therange of the base station, communications take place from the cellularterminal to the wide area cellular network. The communications throughthe base station occur at a selected frequency (channel) within thespectrum of the wide area cellular network, but at the lower billingrates of the wire telephone network, and can occur without adding to theload on the wide area cellular network.

The activation means of the base station may also detect a communicationfrom the cellular terminal received by the radio transceiver at aselected frequency within the spectrum of the wide area cellular networkand generate an OFF-HOOK indication to the wire telephone network inresponse thereto. The base station thus supports both routing of callsfrom the wire network to the cellular terminal and routing of calls fromthe cellular terminal to the wire network.

Same channel interference between the wide area cellular network and thebase station is reduced by selecting an available channel within thecellular spectrum for communications between the cellular terminal andthe base station when the cellular terminal is within range of the basestation. The selected channel utilizes one of the frequencies of thewide area cellular network which is not allocated to the cell of thewide area cellular system in which the base station is located.

In one embodiment of the present invention, a frequency indicatingsignal is received by the base station or the cellular terminal from thewide area cellular network operator over the wire telephone network,responsive to a request from the base station or the cellular terminal.This allows the network operator to assign frequencies for base stationswhich minimize same channel interference with the wide area cellularnetwork. The system carrier also can obtain additional revenue fromunused frequencies within a network cell by leasing these frequenciesfor base station operation within the cell. The frequency assignmentrequest may be initiated automatically upon application or reapplicationof power to the base station. Alternatively, manual user interventionmay be required.

In another aspect of the present invention, the base station detects ifthe electrical connection of the wire telephone network to the wiretelephone network connector has been lost and prevents the transceiverfrom transmitting at the previously selected frequency if the connectionhas been lost. This prevents a base station from being disconnected andreinstalled in a new location where the previously selected frequencycould interfere with frequencies in use in that area by the wide areacellular network. Optionally, this detection and disable aspect respondsto loss of both the power and telephone connections rather than justloss of the telephone connection or power connection.

A method for allocating a frequency to the base station is alsoprovided. The wide area cellular network is notified of the location ofthe base station via the wire network and a frequency is requested fromthe wide area cellular network via the wire network. An indication ofthe requested frequency is received from the wide area cellular networkvia the wire network and is preferably stored in the base station. Anindication of the received frequency is then transmitted to the cellularterminal and preferably stored in the cellular terminal. The request mayoptionally be initiated by the base station by calling the wide areacellular network using a predetermined service number. Such a call maybe initiated by a user input to the base station. Alternatively, thecall may be initiated automatically, by determining if the telephoneconnection or the telephone and power connections to the base stationhave been lost since the indication of the requested frequency was lastreceived. If so, the steps to acquire a new selected frequency forcommunications between the base station and the cellular terminal arerepeated. Communications between the base station and cellular terminalare thereby provided, using the wide area cellular spectrum, withreduced likelihood of frequency overlap and without the need for ahybrid system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B schematically illustrate a radio personal communicationssystem including a base station and a cellular terminal, with radiocommunications between the terminal and the base station, and radiocommunications between the terminal and a wide area cellular network,respectively.

FIG. 2 illustrates a front perspective view of an embodiment of a basestation of the present invention, with a terminal shown in hidden lines.

FIG. 3 is a schematic block diagram of a base station according to thepresent invention.

FIG. 4 is a schematic block diagram of a base station transceiveraccording to the present invention.

FIG. 5 is a schematic block diagram of a radio personal communicationscellular terminal according to the present invention.

FIG. 6 is a flowchart illustrating operations during initialization of aradio personal communications system according to the present invention.

FIG. 7 is a schematic illustration of a first cell re-use pattern for awide area cellular network.

FIG. 8 is a schematic: illustration of a second cell re-use pattern fora wide area cellular network illustrating a method of allocating basestation frequency according to the present invention.

FIG. 9 is a flowchart illustrating operations of a radio personalcommunications system according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art.

Referring now to FIGS. 1A and 1B, conceptual diagrams of a radiopersonal communications system according to the present invention areshown. Such a system operates within a cellular communications networkwhich allocates portions of a plurality of frequencies (channels) withina spectrum to separate geographic cells. Thus, the system provides awide area wireless communications network having the capacity to providehigh quality wireless communications to a large number of users with alimited number of frequencies allocated to the wide area cellularnetwork. As shown in FIG. 1A, a wide area cellular network includes atleast one radio network cell station 102, such as a cellular telephonecell station, for transmitting and receiving messages in a network cellrange indicated by 104, via cell antenna 106. The range 104 of radionetwork cell station 102 is typically represented graphically asillustrated in FIGS. 1A, 1B, 7 and 8. Radio network cell station 102also interfaces with the wire network 108. It will be understood bythose having skill in the art that a wide area cellular network 100typically includes many radio network cell stations 102 to cover a largearea as illustrated in FIGS. 7 and 8. In such a system each radionetwork cell station 102 covers a cell (range) 104 within wide areacellular network 100 and may interface with a central station (notshown) by wireless (radio) communications. The central station mayprovide the connection to wired network 108 for all of the network cellstations 102 that make up wide area cellular network 100.

Still referring to FIG. 1A, a telephone base station 110 is locatedwithin the cell (range) 104 of a network cell station 102 of wide areacellular network. Base station 110 includes a low power transceiver fortransmitting and receiving via base station antenna 112, over a limitedbase station range 114, typically on the order of tens of meters. Thus,a base station may be used for transmission and receipt of radiopersonal communications in a home or office. Base station 110 also iselectrically connected to the wire network 108. Wire network 108, isalso referred to as the Public Switched Telephone Network (PSTN). PSTN108 is the regular "wire line" telephone system supplied by, forexample, the regional Bell Operating Companies, and may use copper wire,optical fiber or other stationary transmission channels. Base station110 may be wired directly to PSTN 108 or connect through a PABX (notshown).

Still referring to FIG. 1A, a radio personal communications terminal 120is shown for radio communications with both base station 110 and radionetwork cell station 102 via antenna 122. Radio personal communications(cellular) terminal includes a radio telephone such as a cellular phone.Cellular terminal 120 may also include, for example, a full computerkeyboard and display, a scanner, and full graphics and multimediacapabilities.

As illustrated in FIG. 1A, when terminal 120 is in the range 114 of thebase station 110, a radio link 124 therebetween is established. As shownin FIG. 1B, when the terminal 120 is outside the range 114 of the basestation 110, but within the range (cell) 104 of the network cell station102, a new radio link 126 is automatically established with the networkcell station 102 to establish communications through wide area cellularnetwork 100. Thus, when the user is relatively close to the base station110 (i.e. within the home or office), wireless communications take placewith the base station so that wide area cellular network, with itshigher billing rate structure, is bypassed. When the user is relativelyfar from the base station 110, communications take place with thecellular network.

It will be understood by those having skill in the art that a completeradio personal communications system will typically include many basestations 110, terminals 120 and radio network cell stations 102. It willalso be understood by those having skill in the art that conventionalcommunications and handoff protocols may be used with the presentinvention, and need not be described further herein. For purposes ofthis description, it will be assumed that the spectrum allocation forthe radio network cells is the IS-54B cellular phone spectrum allocationwhich is illustrated in Table 1 below.

                  TABLE 1                                                         ______________________________________                                        Band-      Number   Boundary  Transmitter Center                              width      of       Channel   Frequency (MHz)                                 System (MHz)   Channels Number  MOBILE  BASE                                  ______________________________________                                        Not Used       1                (824.010)                                                                             (869.010)                             A*     1       33       991     824.040 869.040                                                       1023    825.000 870.000                               A      10      333      1       825.030 870.030                                                       333     834.990 879.990                               B      10      333      334     835.020 880.020                                                       666     844.980 889.980                               A'     1.5     50       667     845.010 890.010                                                       716     846.480 891.480                               B'     1.5     83       717     846.510 891.510                                                       799     848.970 893.970                               ______________________________________                                        Transmitter                                                                           Channel Number Center Frequency (MHz)                                 ______________________________________                                        MOBILE   1 ≦ N ≦ 799                                                                   0.030 N + 825.000                                               990 ≦ N≦ 1023                                                                 0.030 (N - 1023) + 825.000                             BASE     1 ≦ N ≦ 799                                                                   0.030 N + 870.000                                               990 ≦ N≦ 1023                                                                 0.030 (N - 1023) + 870.000                             ______________________________________                                    

In the radio personal communications system described in FIGS. 1A and1B, it is important to avoid same channel interference between basestation 110 and the radio network cell station 102. Same channelinterference can be avoided by using two discrete spectra for thenetwork calls and for the base station. For example, the base stationcan use cordless telephone protocols. Unfortunately, this requires theterminal 120 to operate under both cellular and cordless protocols,which may be costly and wasteful.

According to the invention, the operator of network 100, which hastypically been assigned the use of a specific plurality of frequencieswithin a frequency spectrum of a designated geographic region by aregulatory authority, is allowed to assign frequencies and optionallypower levels, of base station 110. The wide area cellular networkoperator (provider) can assign frequencies and optionally power levelsto base station 110 to minimize same channel interference and tomaximize revenue from the assigned frequency spectrum.

According to the invention, base station 110 uses the obtained frequencyand power level, respectively, to govern operation of base station 110.Frequency and power level signals may also be used to control operationof the radio personal communications (cellular) terminal 120 as will bedescribed below. As will also be described below cellular terminal 120may be controlled to operate at the same frequency and power level asbase station 110. Alternatively, a different frequency and power levelmay be provided. Thus, the wide area cellular network operator canreceive revenue from the use of the frequency, and simultaneouslyprevent radio communications between base station 110 and terminal 120from interfering with communications within cellular network 100.

An embodiment of a base station and cellular terminal according to thepresent invention is illustrated in FIG. 2. Base station 110 includeshousing 130 which is adapted to cooperatively mate with cellularterminal 120 and provide an electrical interface between base station110 and cellular terminal 120 using electrical connector 132 or otherelectrical connecter means. Base station 110 is connected to a powersource (power outlet) by power line connector 134 or other powerconnection means and to a wire telephone network by a wire telephonenetwork connector 136 extending from base station 110 to within housing130 or other means for electrically connecting base station 110 to awire telephone network. As shown in FIG. 2, housing 130 is preferablyportable to allow the user to move it and reinstall it in differentlocations. Base station 110 as illustrated in FIG. 2 may further includebattery charger connector 138 or other charger interface means whichconnects battery powered cellular terminal 120 to a battery charger (notshown in FIG. 2) when cellular terminal 120 is inserted or parked inhousing 130 as illustrated by hidden lines in FIG. 2. Sensor 140 detectswhen cellular terminal 120 is parked in housing 130 and the batterycharger is activated to charge the battery of battery powered cellularterminal 120. It will be understood by those having skill in the artthat a separate sensor 140 need not be used to detect when terminal 120is parked in housing 130.

Base station 110 as illustrated in FIG. 2 also includes display 142 orother user indicating means. Alternatively, cellular terminal 120 mayinclude an indicating means which may be used to display signals frombase station 110 transmitted over electrical connector 132 when cellularterminal 120 is parked in housing 130. Base station 110 may also includekeyboard 144 or other user input means. Alternatively, as with display142, cellular terminal 120 may include an input means which may be usedto provide inputs to base station 110 when cellular terminal 120 isparked in housing 130.

A block diagram of an embodiment of a base station 110 of the presentinvention is illustrated in FIG. 3. Power supply 150 is connected topower line connector 134 and provides the power supply voltages to thecircuitry of base station 110. Power supply 150 further includes powerdetection means 151 for detecting when the connection of power lineconnector 134 to the power source has been lost and for providing asense signal to control processor 154 indicating that power has beenlost.

Ringing current and exchange battery voltage detector 152 iselectrically connected to wire telephone connector 136 and includesmeans for detecting an incoming call on wire telephone connector 136which is connected to wire telephone network 108. Detector 152 furtherdetects if the electrical connection of wire telephone network 108 toconnector 136 has been lost. Detector 152 supplies signals to controlprocessor 154 when an incoming call "ring" is detected and when theconnection to wire telephone network 108 is lost. An indication that thewire telephone network (line) connection has been lost may then be sentto display 142 under the control of control processor 154.

Control processor 154, in cooperation with ringing current and exchangebattery voltage detector 152 provide activation means for initiatingcommunications between wire telephone network 108 and cellular terminal120 through base station 110 when cellular terminal 120 is within region114. For incoming calls from wire telephone network (line) 108, detector152 detects the incoming call and sends an activation signal to controlprocessor 154 which in turn controls subsequent communicationsoperations of base station 110. For calls initiated from cellularterminal 120, control processor 154 detects the communication fromcellular terminal 120 received by transceiver circuit 164 or other radiotransceiving means connected to antenna 112 at a selected frequencywithin the spectrum of wide area cellular network 100. Control processor154 sends a control signal to detector circuit 152 to generate OFF-HOOKand other signals such as pulse dialling that may be necessary tointerface with a loop-disconnect line interface such as is typicallyused by wire telephone network 108.

Splitter circuit 156 effects a split of the two-wire, bidirectionaltelephone audio signal into a four-wire system of separate send andreceive signals. Received signals from the wire telephone network 108are converted from analog to digital by analog to digital converter (Ato D) 158 while transmit signals to wire telephone network 108 areconverted from digital to analog by digital to analog converter (D to A)160. This allows all of the subsequent audio signal processing to becarried out digitally using digital signal processors. Echo canceler 162attenuates echoes of the signal sent through connector 136 to PSTN wirenetwork 108 to inhibit corrupting of the signal received from the PSTN.Echo canceler circuit 162 further prevents echoes being transmitted tocellular terminal 120 by transceiver circuit 164 or other radiotransceiving means connected to antenna 112.

On incoming calls over wire telephone network (line) connector 136,transceiver circuit 164 responds to the ring detect from detector 152under the control of processor 154 to communicate with cellular terminal120 using a selected frequency within the frequency spectrum of the widearea cellular network 100. Storage circuit 155 or other storage means iselectrically connected to control processor 154 to provide a storagecapacity for program and data information such as a frequency indicatingsignal representing the selected frequency. Storage circuit 155 mayinclude conventional readable and writable memory such as RAM or EEPROM.

After echo cancellation, modem 166 processes received digitized audiosignals to extract any digital control messages that might be receivedalong with the audio signal from the wire telephone network (line). Suchdigital control messages may, for example be programming information forbase station 110 transmitted by the operator of wide area cellularnetwork 100. Extracted digital control messages are passed to controlprocessor 154. Modem 166 may perform data/speech discrimination. Adigital signal processor such as Texas Instruments type TMS320C56 may beused for echo canceler 162 and modem 166.

Received digitized speech is passed to transceiver 164 for transmission.The digitized speech may first be compressed by compression circuit, notshown, to a lower bit rate using a conventional speech decodingalgorithm such as CELP or VSELP. In an analog transmission embodiment ofbase station 110 of the present invention a conversion circuit, notshown, reconverts the discriminated speech to an analog signal formodulating transceiver 164 which in this embodiment is an analogtransceiver.

Radio signals from cellular terminal 120 to base station 110 received byantenna 112 are detected and converted to digital speech signals bytransceiver 164. The digital speech signals are then passed to echocanceler circuit 162 and modem circuit 166 for transmission on wiretelephone network (line) connector 136 to wire network 108.Alternatively, the received signals may be digitized to complex numberform, using for example the LOGPOLAR technique described in U.S. Pat.No. 5,048,049. The complex number stream is then passed to modem 166 fornumerical demodulation and conversion to analog speech for sending onthe wire telephone line.

The present invention may also be used for data transmission fromcellular terminal 120 when cellular terminal 120 either incorporates apersonal computer system or by plugging cellular terminal 120 into apersonal computer to connect the computer to modem circuit 166 withoutthe use of a direct wire telephone line cable connection to thecomputer. When handling data transmissions, modem circuit 166 andtransceiver 164 translate the data stream between the over-the-airprotocols used and normal wire telephone line data transmissionprotocols. Transceiver 164 may also detect when the received signal hasreverted to voice and, responsive to control processor 154, effect areversion of modem circuit 166 and echo canceler circuit 162 to theprocessing of voice signals.

Transceiver 164 may be selected to generate and receive signalsconforming to any standard, for example, AMPS, ETACS, NMT450, NMT900,GSM, DCS1800 or IS54. In addition, transceiver 164 may generate orreceive signals conforming to air-interface standard for communicationswith satellite systems, such as INMARSAT-M, INMARSAT-P, IRIDIUM,ODYSSEY, GLOBALSTAR, ELLIPSAT or M-SAT. All such standards may beutilized with the present invention to provide communications fromcellular terminal 120 through normal PSTN wire lines 108 and avoidingusing the wide area system.

FIG. 4 illustrates a schematic block diagram of a radio transceiver 164of FIG. 3. As shown, transceiver 164 includes circuitry for both thereception and transmission of the radio frequency signals. Signalsreceived by the antenna 112 are directed to the receive circuits by theduplexer 201. The duplexer is a filter with two separate bandpassresponses: one for passing signals in the receive band and another forpassing signals in the transmit band. Duplexer 201 allows simultaneoustransmission and reception of signals by using different receive andtransmit frequencies. For example, in the ADC architecture, the receiveand transmit frequencies are separated by 45 MHz.

After passing through the duplexer 201, received signals are amplifiedby a low noise radio frequency (RF) amplifier 202. This amplifierprovides just enough gain to overcome the expected losses in the frontend circuitry. After amplification, unwanted components of the signalare filtered out by the receive filter 203. After filtering, the signalis mixed down to a first intermediate frequency (IF) by mixing it inmixer 204 with a second signal generated by the channel synthesizer 215and filtered by Local Oscillator (LO) filter 214. The first IF signal isthen amplified by amplifier 205 and unwanted mixing products are removedby IF filter 206. After filtering, the first IF is mixed in mixer 207 toyet another lower frequency or second IF signal, using a signal providedby local oscillator synthesizer 216. The second IF signal is thenfiltered by two filters 208 and 210, and amplified by multistageamplifiers 209 and 211 to obtain an IF signal 212 and a radio signalstrength indication (RSSI) signal 213. Thereafter, it undergoes aprocess of detection, for example, as described in U.S. Pat. No.5,048,059 to Dent, the disclosure of which is incorporated herein byreference.

In order to transmit, a datastream 219 is generated by modem 166 (FIG.3). In ADC architecture, the datastream is organized as bursts for timedivision multiplexing with other users. Reference oscillator 218generates a precise frequency which is used as a stable reference forthe RF circuits. The output of oscillator 218 is passed through amultiplier 221 where it experiences a sixfold increase in frequency.This frequency is then passed into a quadrature network 222 whichproduces two signals of equal amplitude which have a quadrature phaserelationship, i.e. they are offset by 90°. These quadrature signals,along with the datastream 219, are combined in the modulator 223 tocreate a modulated signal, as described in an article entitled I and QModulators fox Cellular Communications Systems, D. E. Norton et al.,Microwave Journal, Vol. 34, No. 10, October 1991, pp. 63-79. Themodulated signal is passed to a mixer 224 which translates the signal toradio frequency. The exact radio frequency is determined by the localoscillator signal provided by the channel synthesizer 215. The radiofrequency signal is passed through a variable gain controlled amplifier225. The gain of this amplifier, which is controlled by means of avoltage on transmit power control line 220, determines the eventualoutput power, since the linear power amplifier 227 has fixed gain.Filtering is performed by transmit filter 226.

Referring now to FIG. 5, the design of terminal 120 is similar to thatof base station 110 (FIG. 3) except that a ringing current and exchangebattery voltage detector 152 are not present. As illustrated in FIG. 5,cellular terminal 120 includes transceiver 250 or other means forcommunicating with wide area cellular network 100 when cellular terminal120 is not within the base region (range) 114 of base station 110 andfor communicating with transceiver 164 of base station 110 when cellularterminal 120 is within base region 114. Transceiver 250 is connected toantenna 122. Cellular terminal 120 further includes its own controlprocessor 254 and storage means 255 similar to those described withrespect to base station 110 and transmit circuit 251 and receive circuit253 for receive and transmit signal processing respectively.

As further shown in FIG. 5, when terminal 120 is a cellular phone, itincludes a keypad 257, a display 259, a speaker 261, and a microphone263. In order to provide a computer communications terminal for receiptand transmission of audio, video and data and/or multimedia signals,keypad 257 may be a full scale personal computer keyboard and display259 may be a large graphics display. A scanner 265 may also be providedas may other devices 267 such as disk drives and modems. The design ofterminal 120 is well known to those having skill in the art and need notbe described further herein.

As described above, radio communications between base station 110 andcellular terminal 120 occurs at a frequency assigned by the wide areacellular network provider to avoid same channel interference betweenbase station 110 and network cell station 102. In the embodiment of thepresent invention described above, the channel selection means whichobtains the channel within the cellular spectrum of wide area cellularnetwork 100 for communications between cellular terminal 120 and basestation 110 is included in base station 110. For non-multiplexedsystems, any given frequency is one channel; however, for multiplexedtype systems each frequency may carry multiple communications channels.The present invention will be further described referring to frequency,however, it is to be understood that in a multiplexed system basestation 110 may be assigned a specific channel or slot using suchselected frequency.

The selected frequency may be entered into base station 110 fromexternal to base station 110 as an extracted digital control message, asdescribed above, in which case the frequency indicating signal isreceived by base station 110 by wire line communications over connector136. The frequency indicating signal is converted to a synthesizercommand and applied to line 217 to produce the requisite transmit andreceive frequency. The power level indicating signal is converted to atransmit power control signal and applied to line 220 to control thetransmit power. The conversions are preferably performed by controlprocessor 154 using conventional techniques. Operations performed to setthe frequency, and optionally power level, will be described below inconnection with FIG. 6.

The frequency indicating signal from the operator of wide area network100 is selected to minimize interference between base station 110 andnetwork cell station 102. Preferably, a frequency is utilized which isone of the frequencies within the cellular spectrum which is notallocated to the network cell station 102 in the cell 104 in which basestation 110 is located. More preferably, a frequency is selected fromthe group of frequencies within the cellular spectrum which is allocatedto a cell of wide area cellular network 100 which is farthest from saidbase station as illustrated in FIGS. 7 and 8.

The circuitry of base station 110 as illustrated in FIG. 3 furtherfunctions as a requesting means within housing 130, electricallyconnected to wire telephone line connector 136, for communicating withthe operator of wide area network 100 over wire network 108 using apredetermined service number stored in storage circuit 155. Controlprocessor 154 initiates a call using the predetermined service number bysending control and a data signals representing a request. Modem 166 andconverter 160 are used to transmit the request over line 136 as a knowntype of carrier which may be detected by a modem (not shown) set up forthis purpose by the operator of wide area cellular network 100. Theoperator of wide area cellular network assigns a frequency manually orautomatically, to reduce or avoid frequency interference. The requestedfrequency indicating signal from the operator of wide area cellularnetwork 100 is then received by modem 166 and an extracted digitalcontrol message is provided to control processor 154 as described above.An indication of the selected frequency is stored in storage circuit155, based upon the received frequency indicating signal. Alternatively,frequencies can be assigned via a removable frequency indicator, such asa "smart card" as described in copending application Ser. No. 08/093,076to Rydbeck entitled Method and Apparatus for Controlling TransceiverOperations in a Radio Communication System, assigned to the assignee ofthe present application, the disclosure of which is hereby incorporatedherein by reference.

A frequency indicating signal is also provided to cellular terminal 120when terminal 120 is parked in base station 110 and stored in storagemeans 255 as an indication of the selected frequency so that bothcellular terminal 120 and base station 110 have the selected frequencyinformation. Alternatively, the frequency information may be provided tocellular terminal 120 using the wide area cellular network 100 ifcellular terminal 120 is not parked in base station 110 and the userdoes not wish to park the terminal before initiating communicationsbetween base station 110 and cellular terminal 120 following a change inthe selected frequency.

The process of requesting a frequency indicating signal may be initiatedby the operator as an input using keyboard 144, for example, by pressing#0 to initiate calling the predetermined service number. Alternatively,the request may be initiated by control processor 154 responsive to alost connection signal from detector 152. The lost connection signal mayindicate that the connection of wire telephone line 136 to wiretelephone network 108 has been lost or that both the telephoneconnection and the power connection, based on the signal from powerdetection means 151 to control processor 154 have been lost, asdescribed above. Thus, the detector 152, power detection means 151 andcontrol processor 154 determine when a new frequency selection isrequired and initiate such a request.

Alternatively, the selected frequency information may be entered intobase station 110 using keyboard 144 which would likewise pass theinformation to control processor 154. This allows the user of basestation 110 to separately obtain the selected frequency information fromthe operator of wide area cellular network 100 and then manually inputthe data through keyboard 144.

The means for requesting and receiving the frequency indicating signalmay also be contained in cellular terminal 120. If this is the case,cellular terminal 120 may contact the operator of wide area cellularnetwork either through network cell station 102 or using telephone lineconnector 136 while cellular terminal 120 is parked in base station 110.Likewise, the input means for manually entering the request for afrequency indicating signal may be keypad 257 of cellular terminal 120.

If base station 110 is moved to a new location, any selected frequencypreviously used may be invalid and likely to cause interference withwide area cellular network 100 if transmissions from base station 110are allowed to occur without obtaining a new selected frequency from theoperator of wide area cellular network 100. It is desirable that basestation 110 include means responsive a detected loss of telephoneconnection or telephone and power connection loss as described above forpreventing transmission by transceiver 164 using the previously selectedfrequency. This may be readily accomplished by the circuitry illustratedin FIG. 3, as control processor 154 receives indicating signals fromboth detector circuit 152 and power detection means 151 which togetheract as a means for detecting loss of telephone and/or power connection.Control processor 154 may then control transceiver 164 to preventfurther transmissions. Control processor 154 may further send anindication to display 142 indicating that a new frequency needs to beobtained. Control processor 154 may also send a message to the operatorof the wide area cellular network via the PSTN network.

Initialization and channel acquisition operations of an embodiment ofthe personal communications system of the present invention areillustrated in the flow chart of FIG. 6. Operations are initialized atblock 300 when base station 110 is obtained by the user and plugged intoa normal domestic telephone jack with telephone connector 136 and poweroutlet with power connector 134. On power up, detector 152 notifiescontrol processor 154 that a telephone connection has been establishedto wire telephone line 108 and power sense signal from power detectionmeans 151 notifies control processor 154 that line power has beenconnected. At block 302 base station 110 calls the wide area cellularnetwork using a predetermined service number. The service number can bestored in base station 110, requiring only one or two keypad depressionson keyboard 144 to effect dialling or may be initiated automatically asdescribed above. Alternatively, as described above, the user may contactthe wide area cellular provider using a different phone and PSTN lineand verbally request set-up information which may then be manually keyedinto base station 110. The service number can appropriately be an "800"type number that is valid from all locations.

After the call is initiated at block 302, base station 110 notifies thewide area cellular network operator of the location of base station 110at block 304. Using signalling facilities available in modern digitaltelephone networks, this may be accomplished by having the wide areacellular network operator request from the PSTN the number of the phoneline originating the call. At block 306 base station 110 requests acontrol message including a frequency, from the wide area cellularnetwork operator. The request may also include power level and channelinformation as well as frequency. At block 308 base station 110 receivesa control message including an indication of the requested frequencyfrom the wide area cellular network operator. This is then stored as anindication of the received frequency in base station 110 at block 310.

Base station 110 then transmits an indication of the received frequencyto cellular terminal 120 at block 312. This transmission may beaccomplished when cellular terminal 120 is parked in base station 110using system connector 132. Alternatively, a frequency indicating signalmay be transmitted by radio communications using transceiver 164 ifcellular terminal 120 is not parked in base station 110. Such atransmission may be made using the last frequency assigned to basestation 110 by the cellular network operator. Optionally, when it isnecessary to reallocate the base frequency when cellular phone 120 isnot parked in base station 110, the wide area network operator may placea call to cellular phone 120 over the cellular network and send a datamessage informing cellular terminal 120 of the change to the basefrequency. However, if the base frequency will not be frequentlyreallocated, base station 110 may notify the user of the need to parkcellular terminal 120 to obtain the new frequency information bydisplaying a warning message on display 142. At block 314 cellularterminal 120 stores an indication of the received frequency in cellularterminal 120.

Once the operating frequency for communications between base station 110and cellular terminal 120 has initially been established, the assignedfrequency will continue to be valid so long as base station 110 remainsin the same location. However, should base station 110 be moved to a newlocation, interference with the wide area cellular network could resultas the previously assigned frequency for base station 110 may be used inthe local cell of the wide area cellular network where base station 110is reinstalled. Consequently, at block 316 base station 110 determinesif the telephone connection to the base station has been lost since theindication of the requested frequency was last received as describedabove. Base station 110 may further determine if the power connection tobase station 110 has been lost since the indication of the requestedfrequency was last received. If the telephone connection or,alternatively, the telephone and power connections have been lost sincethe indication of the requested frequency was last received, basestation 110 repeats steps 300 through 314 as described above.Alternatively, at step 316 when it has been determined that theconnections have been lost base station 110 communications may bedisabled until a new request for a selected frequency is initiated.

The above operations were described for an embodiment using the basestation processor and keyboard to acquire the frequency information. Inan alternative embodiment the keyboard and processor of cellularterminal 120 may be used to carry out the initialization operations. Inthis embodiment, all of the steps of FIG. 6 would be carried out whilecellular terminal 120 was parked in base station 110. The communicationswith the wide area cellular network operator could then be handled bycellular terminal 120 with base station 110 serving to transmit signalsbetween cellular terminal 120 and the network operator over PSTN 108.

It is preferred that base stations 110 not be allocated frequencies thatare already in use in the cell of the wide area cellular network inwhich base station 110 is located, but to choose frequencies in use inthe cell which is a maximum distance away. Allocation of frequency bythe wide area cellular network provider in one embodiment is illustratedin FIG. 7. FIG. 7 illustrates a 21-cell frequency reuse pattern which isemployed in some United States wide area cellular networks to avoidinterference between neighboring cells. It is to be understood that awide area cellular network 100 may include a plurality of such reusepatterns, and thus include greater than the 21 cells illustrated in FIG.7. Each cell 104 in a cluster of 21 uses a different 1/21 fraction ofthe total number of frequencies available to the wide area cellularprovider. FIG. 7 shows the distribution of 21 groups of frequenciesnumbered 1 to 21 in a regularly spaced cell lattice. It may be seen thatthe cells using the same frequency groups are equispaced and root(21 )cell diameters between centers where cell diameter is defined as thediameter of the inscribed circle of each hexagon.

It may be seen in FIG. 7 that cells numbered 15 or 8 are those mostdistant from the cells numbered 1. Therefore, the frequencies thatshould be used for base stations 110 located within cells numbered 1should be drawn from frequency groups 8 and 15. Reciprocally, thefrequencies used for base stations 110 located in cells numbered 15should be drawn from frequency groups 1 and 8 and so on for cellsnumbered 8. By symmetry, base stations 110 in cells numbered 2 shoulduse frequencies drawn from groups 9 and 16 and so forth. Thus, basestations 110 within each region may employ 2/21 of the total number offrequencies available. If this contains at least 21 frequencies, then a21-cell re-use plan can be employed to ensure that cells using the samefrequency are at least root(21) cell diameters apart. This requires thatthe total number of frequencies employed in both the cell and cellsystems is at least 21×21/2=220. This condition is normally satisfied inthe U.S. AMPS system, where two competing operators share over 800channels, having more than 400 each. Thus it is desirable that the cellsshould be capable of being programmed and reprogrammed to optimumfrequencies from the mobile telephone network according to the cell inwhich they are located.

FIG. 8 illustrates how base frequency allocations may be made in thecase of a cell re-use pattern such as the tighter, 7-cell pattern suchas may be employed in the European GSM system. As shown in FIG. 8,within each cell, different areas are allocated different sets offrequencies for use by base stations 110 located within thosesubregions. In FIG. 8, the frequency allocation patterns for basestations 110 are illustrated for the cells numbered 1 and 5respectively.

FIG. 9 illustrates a method for operation of the radio personalcommunications system once the frequency information has been acquiredby base station 110 and its associated cellular terminal 120. Operationsbegin when power is applied to cellular terminal 120 at Block 352. Uponapplication of power, cellular terminal 120 scans the selected frequencyallocated to its associated base station 110 at Block 354, anddetermines if a signal level above threshold has been detected, at Block356. If a signal level above threshold has been detected, then terminal120 is within the range 114 of its associated base station 110. Cellularterminal 120 then communicates at Block 360 over PSTN 108 by wirelesscommunications to base station 110. If a signal level above thresholdwas not detected, then the terminal 120 is not within the range 114 ofbase station 110 and communications are initiated with network cellstation 102 at Block 358, using conventional techniques.

It will be understood by those having skill in the art that a separatevoice channel frequency and power level may be used for transmissions bybase station 110 and terminal 120. The power levels may be different forthe base station and the terminal if, for example, the base station hasa larger antenna or a more sensitive receiver. It is also contemplatedthat the frequencies will be different since the terminal and basestation would not typically transmit or receive on the same frequenciesin a duplex transceiver. Alternatively, a single frequency and powerlevel may be obtained from the wide area circular provider and a secondfrequency and power level may be determined from the single frequencyand power level.

Accordingly, the network provider/operator may allocate frequencies andpower levels of base station-to-terminal communications. By allocatingthe frequency and power level of base station-to-terminalcommunications, same frequency interference within a network cell isreduced and the network provider obtains additional revenue from thelicensed frequency spectrum for the base station.

While the invention has been described with specificity above primarilyin terms of allocated frequencies, it is to be understood that thepresent invention is likewise directed to systems utilizing any form ofmultiplexing wherein a single frequency carries a plurality of channels.In such a system, the present invention obtains from the external sourcesuch as the wide area cellular network operator both assigned frequencyinformation and the specific channel slot within the assigned frequency.It is also to be understood that the present invention may be usedwithin any cellular type wireless communications structure where acellular type structure is understood to encompass any systemincorporating any type of channel reuse pattern over a wide areacommunications network.

In the drawings and specification, there have been disclosed typicalpreferred embodiments of the invention and, although specific terms areemployed, they are used in a generic and descriptive sense only and notfor purposes of limitation, the scope of the invention being set forthin the following claims.

That which is claimed:
 1. A radio personal communications system foroperation within a wide area cellular network, which uses a plurality offrequencies within a spectrum, and within a base region linked to a wiretelephone network, which base region overlaps with said cellularnetwork, comprising:a battery powered radio terminal operating withinthe cellular spectrum; a telephone base station located within said baseregion and connected to said wire telephone network; said telephone basestation including power line connecting means; detecting meanselectrically connected to said power line connecting means for detectingif the electrical connection of said power line connecting means to anexternal power source has been lost; channel selecting means within atleast one of said radio terminal and said telephone base station, andresponsive to said detecting means, for selecting an available channelwithin said cellular spectrum for communications between said radioterminal and said telephone base station when said radio terminal iswithin said base region; said telephone base station further comprisingfirst transceiving means, electrically connected to said wire telephonenetwork, and responsive to said channel selecting means, forcommunicating with said radio terminal using said selected channel whensaid radio terminal is within said base region; and said radio terminalfurther comprising second transceiving means, for communicating withsaid wide area cellular network when said radio terminal is not withinsaid base region and for communicating with said first transceivingmeans using said selected channel when said radio terminal is withinsaid base region; wherein said channel selecting means is containedwithin said radio terminal and wherein said telephone base stationcomprises means for receiving said radio terminal and providing anelectrical interface with said channel selecting means.
 2. A radiopersonal communications system as in claim 1 further comprising meanswithin at least one of said radio terminal and said telephone basestation, responsive to said detecting means, for preventing transmissionby said first transceiving means after the electrical connection of saidpower line connecting means to an external power source has been lostuntil said channel selecting means selects an available channel withinsaid cellular spectrum.
 3. A radio personal communications system as inclaim 1 wherein said detecting means further comprises means fordetecting that a connection between said telephone base station and saidwire telephone network has been established and wherein said channelselecting means selects said available channel from one of saidfrequencies which is not allocated to the cell of said wide areacellular network in which said telephone base station is located.
 4. Aradio personal communications system for operation within a wide areacellular network, which uses a plurality of frequencies within aspectrum, and within a base region linked to a wire telephone network,which base region overlaps with said cellular network, comprising:abattery powered radio terminal operating within the cellular spectrum; atelephone base station located within said base region and connected tosaid wire telephone network; means within at least one of said radioterminal and said telephone base station, for detecting that the wiretelephone network connection to said telephone base station has beenlost; channel selecting means within at least one of said radio terminaland said telephone base station, for selecting an available channelwithin said cellular spectrum for communications between said radioterminal and said telephone base station when said radio terminal iswithin said base region; said telephone base station further comprisingfirst transceiving means, electrically connected to said wire telephonenetwork, and responsive to said channel selecting means, forcommunicating with said radio terminal using said selected channel whensaid radio terminal is within said base region; said radio terminalfurther comprising second transceiving means, for communicating withsaid wide area cellular network when said radio terminal is not withinsaid base region and for communicating with said first transceivingmeans using said selected channel when said radio terminal is withinsaid base region; and means within at least one of said radio terminaland said telephone base station, responsive to said detecting means, forpreventing transmission by said first transceiving means after the wiretelephone network connection to said base station has been lost untilsaid channel selecting means selects an available channel within saidcellular spectrum; wherein said channel selecting means is containedwithin said radio terminal and wherein said telephone base stationcomprises means for receiving said radio terminal and providingelectrical contact with said channel selecting means.
 5. A radiopersonal communications system as in claim 4 wherein said telephone basestation further comprises:power line connecting means; battery chargingmeans electrically connected to said power line connecting means.
 6. Aradio personal communications system as in claim 5 wherein saidtelephone base station further comprises a portable housing and whereinsaid first transceiving means is located within said portable housing.7. A telephone base station for connecting a wire telephone network to acellular terminal within a local region of a wide area cellular networkwhich uses a plurality of frequencies within a spectrum,comprising:means for electrically connecting said telephone base stationto said wire telephone network; activating means, connected to saidelectrically connecting means, for detecting an incoming call on saidwire telephone network; means for detecting that a wire telephonenetwork connection to said telephone base station has been established;channel selecting means, responsive to said detecting means, forselecting an available channel within said cellular spectrum forcommunications between said cellular terminal and said telephone basestation when said cellular terminal is within said local region; radiotransceiving means, responsive to said activating means, for initiatingcommunications with said cellular terminal using said selected channelwhen said cellular terminal is within said local region; means forreceiving said cellular terminal and providing an electrical interfacetherewith; and means for providing said available channel to saidcellular terminal through said electrical interface.
 8. A telephone basestation according to claim 7 wherein said channel selecting meansselects said available channel from one of said frequencies which is notallocated to the cell of the wide area cellular network in which saidtelephone base station is located.
 9. A telephone base station accordingto claim 7 wherein said activating means further comprises means fordetecting a communication from said cellular terminal received by saidradio transceiving means at a selected frequency within the spectrum ofsaid wide area cellular network and for generating an OFF-HOOKindication to said electrically connecting means, in response thereto.10. A telephone base station for a radio telephone network operatingwithin a wide area cellular network comprising:a portable housing;means, extending within said portable housing, for electricallyconnecting said telephone base station to a wire telephone network;radio transceiving means in said portable housing; means, in saidportable housing, for receiving an external frequency indicating signal;means, in said portable housing, responsive to said external frequencyindicating signal, for operating said transceiving means at a frequencycorresponding to the received frequency indicating signal; power lineconnecting means extending within said portable housing; detectingmeans, electrically connected to said power line connecting means, fordetecting if the electrical connection of said power line connectingmeans to an external power source has been lost; and means, in saidportable housing, responsive to said detecting means, for preventingtransmission by said radio transceiving means at said frequencycorresponding to the received frequency indicating signal after theelectrical connection of said power line connecting means to an externalpower source has been lost.
 11. A radio personal communications systemfor operation within a wide area cellular network, which uses aplurality of frequencies within a spectrum, and within a base regionlinked to a wire telephone network, which base region overlaps with saidcellular network, comprising:a battery powered radio terminal operatingwithin the cellular spectrum; a telephone base station located withinsaid base region and connected to said wire telephone network; saidtelephone base station including power line connecting means; detectingmeans electrically connected to said power line connecting means fordetecting if the electrical connection of said power line connectingmeans to an external power source has been lost; channel selecting meanswithin at least one of said radio terminal and said telephone basestation, and responsive to said detecting means, for selecting anavailable channel within said cellular spectrum for communicationsbetween said radio terminal and said telephone base station when saidradio terminal is within said base region; said telephone base stationfurther comprising first transceiving means, electrically connected tosaid wire telephone network, and responsive to said channel selectingmeans, for communicating with said radio terminal using said selectedchannel when said radio terminal is within said base region; and saidradio terminal further comprising second transceiving means, forcommunicating with said wide area cellular network when said radioterminal is not within said base region and for communicating with saidfirst transceiving means using said selected channel when said radioterminal is within said base region; wherein said telephone base stationcomprises means for receiving said radio terminal and providing anelectrical interface therewith, and means for providing said availablechannel to said radio telephone through said electrical interface.
 12. Aradio personal communications system for operation within a wide areacellular network, which uses a plurality of frequencies within aspectrum, and within a base region linked to a wire telephone network,which base region overlaps with said cellular network, comprising:abattery powered radio terminal operating within the cellular spectrum; atelephone base station located within said base region and connected tosaid wire telephone network; said telephone base station including powerline connecting means; detecting means electrically connected to saidpower line connecting means for detecting if the electrical connectionof said power line connecting means to an external power source has beenlost; channel selecting means within at least one of said radio terminaland said telephone base station, and responsive to said detecting means,for selecting an available channel within said cellular spectrum forcommunications between said radio terminal and said telephone basestation when said radio terminal is within said base region; saidtelephone base station further comprising first transceiving means,electrically connected to said wire telephone network, and responsive tosaid channel selecting means, for communicating with said radio terminalusing said selected channel when said radio terminal is within said baseregion; and said radio terminal further comprising second transceivingmeans, for communicating with said wide area cellular network when saidradio terminal is not within said base region and for communicating withsaid first transceiving means using said selected channel when saidradio terminal is within said base region; wherein said battery poweredradio terminal comprising means for receiving said available channelwithin said cellular spectrum for communications between said radioterminal and said telephone base station from said wide area cellularnetwork over said second transceiving means.
 13. A radio personalcommunications system for operation within a wide area cellular network,which uses a plurality of frequencies within a spectrum, and within abase region linked to a wire telephone network, which base regionoverlaps with said cellular network, comprising:a battery powered radioterminal operating within the cellular spectrum; a telephone basestation located within said base region and connected to said wiretelephone network; means within at least one of said radio terminal andsaid telephone base station, for detecting that the wire telephonenetwork connection to said telephone base station has been lost; channelselecting means within at least one of said radio terminal and saidtelephone base station, for selecting an available channel within saidcellular spectrum for communications between said radio terminal andsaid telephone base station when said radio terminal is within said baseregion; said telephone base station further comprising firsttransceiving means, electrically connected to said wire telephonenetwork, and responsive to said channel selecting means, forcommunicating with said radio terminal using said selected channel whensaid radio terminal is within said base region; said radio terminalfurther comprising second transceiving means, for communicating withsaid wide area cellular network when said radio terminal is not withinsaid base region and for communicating with said first transceivingmeans using said selected channel when said radio terminal is withinsaid base region; and means within at least one of said radio terminaland said telephone base station, responsive to said detecting means, forpreventing transmission by said first transceiving means after the wiretelephone network connection to said base station has been lost untilsaid channel selecting means selects an available channel within saidcellular spectrum; wherein said telephone base station comprises meansfor receiving said radio terminal and providing an electrical interfacetherewith, and means for providing said available channel to said radiotelephone through said electrical interface.
 14. A radio personalcommunications system for operation within a wide area cellular network,which uses a plurality of frequencies within a spectrum, and within abase region linked to a wire telephone network, which base regionoverlaps with said cellular network, comprising:a battery powered radioterminal operating within the cellular spectrum; a telephone basestation located within said base region and connected to said wiretelephone network; means within at least one of said radio terminal andsaid telephone base station, for detecting that the wire telephonenetwork connection to said telephone base station has been lost; channelselecting means within at least one of said radio terminal and saidtelephone base station, for selecting an available channel within saidcellular spectrum for communications between said radio terminal andsaid telephone base station when said radio terminal is within said baseregion; said telephone base station further comprising firsttransceiving means, electrically connected to said wire telephonenetwork, and responsive to said channel selecting means, forcommunicating with said radio terminal using said selected channel whensaid radio terminal is within said base region; said radio terminalfurther comprising second transceiving means, for communicating withsaid wide area cellular network when said radio terminal is not withinsaid base region and for communicating with said first transceivingmeans using said selected channel when said radio terminal is withinsaid base region; and means within at least one of said radio terminaland said telephone base station, responsive to said detecting means, forpreventing transmission by said first transceiving means after the wiretelephone network connection to said base station has been lost untilsaid channel selecting means selects an available channel within saidcellular spectrum; wherein said battery powered radio terminal comprisesmeans for receiving said available channel within said cellular spectrumfor communications between said radio terminal and said telephone basestation from said wide area cellular network over said secondtransceiving means.